A service appliance is installed between production servers running
service applications and service users. The production servers and their
service applications provide services to the service users. In the event
that a production server is unable to provide its service to users, the
service appliance can transparently intervene to maintain service
availability. To maintain transparency to service users and service
applications, service users are located on a first network and production
servers are located on a second network. The service appliance assumes
the addresses of the service users on the second network and the
addresses of the production servers on the first network. Thus, the
service appliance obtains all network traffic sent between the production
server and service users. While the service application is operating
correctly, the service appliance forwards network traffic between the two
networks using various network layers.